The invention relates to a magnetic core, comprising a first lamellar core part of amorphous, ferromagnetic material which is bonded by means of an epoxy adhesive to a second lamellar core part or to a substrate.
Magnetic cores having core parts of amorphous, ferromagnetic material are used, inter alia, in magnetic heads (particularly for video applications) and in transformers. When assembling the core parts to a core, one of the difficulties is to provide a satisfactory bond.
Glass is a frequently used bonding material in conventional magnetic heads. However, glass is not suitable in the present case, because its high processing temperature (higher than 300.degree. C.) is detrimental to the magnetic properties of the amorphous, ferromagnetic metal of the core parts. To prevent deterioration, the bond must be realized in a temperature range below 200.degree. C.
Epoxy compounds are frequently used as bonding agents for bonding metals. The epoxy compounds providing a satisfactory bond have, however, the drawback for the relevant application that they have a high viscosity. This high viscosity prevents the realization of very thin bonding layers. When lamellar cores of amorphous, ferromagnetic material are used in magnetic heads, it is important for the bonding layers between the lamellae to be as thin as possible (particularly thinner than 0.1 .mu.m) in order to obtain an optimum possible writing efficiency. (The thicker the bonding layers are, the less magnetic material remains in the case of a given track width). However, in connection with eddy current losses they must ensure a satisfactory insulation between the core parts. In addition it is important for the bonding layer between head core and substrate to be as thin as possible. If the bonding layer is thick, there will sooner be problems when grinding a tape contact face profile on the head. Chamfers may be produced both on the substrate and on the head core, resulting in spacing losses and/or efficiency losses.
There exist epoxy compounds having a low viscosity and thus providing the possibility of a thin bonding layer. These epoxy compounds have, however, the drawback that they do not satisfactorily bond to an amorphous, ferromagnetic material surface.